RFR (S) 8225437: JvmtiExport::gc_epilogue is unnecessary

[coleen . phillimore]

Summary: Remove jvmtiExport::gc_epilogue after full GCs

See bug for more information.

open webrev at http://cr.openjdk.java.net/~coleenp/2019/8225437.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8225437

Tested with hs-tier1-3.

Thanks,
Coleen